Strange Ornamental Symbol on Bach Piece

Question

This is from the marvelous andante from Bach’s organ trio sonata BWV 528. What does this symbol mean on the stave of the second keyboard? I am assuming it is ornamental. Is it just a strange version of the trill symbol?

_{(click to enlarge)}

Answer 1

That's just a trill, tr. Different engravers over the years have given the symbol various different forms, and that is one in which the "r" is perhaps less obviously an "r," at least to modern eyes.